Sessions, a conservative heavyweight known for his hardline immigration views, backed Trump at a packed rally in a local football stadium here, praising his stance on immigration and trade and calling his campaign a “movement… that must not fade away.”

“The American people are not happy with their government,” Sessions said. “We have an opportunity Tuesday. It may be the last opportunity we have for the people’s voice to be heard.”

The Alabama senator, who has never endorsed a candidate in a Republican presidential primary, repeatedly praised Trump’s position on immigration, which includes his proposal to build a wall on the U.S.-Mexico border and deport illegal immigrants. “You have asked for 30 years, and politicians have promised for 30 years, to fix illegal immigration,” Sessions said. “Donald Trump will do it.”

Sessions is the first sitting U.S. senator to formally endorse Trump, and his decision to back the real estate mogul and former reality-show star is a major blow to Texas Sen. Ted Cruz, one of Sessions’ closest allies in Washington, who had lobbied for his support.

Still Sessions hinted that he didn’t entirely agree with all of Trump’s views. “You know, nobody is perfect. We can’t have everything,” he told the crowd here. But, he added, “I think at this time, in my opinion, my best judgment, at this time in America’s history, we need to make America great again.”

His endorsement came just days after Trump won the backing of his former rival, New Jersey Gov. Chris Christie.

“I am becoming mainstream! All these people are endorsing me!” Trump gleefully declared after the Alabama senator announced his support. “But Sessions… that’s a biggie.”

The endorsements came as Trump heads into Super Tuesday with what seems to be unstoppable momentum. According to polls, the businessman leads in all 10 states voting on Tuesday — except for Texas, where he narrowly trails Cruz. The Trump camp is so confident heading into Super Tuesday that the candidate is spending most of that day campaigning in states such as Ohio and Florida, home turf of his rivals John Kasich and Marco Rubio, where Republicans will vote later this month.

Still, much of the Trump rally here was dedicated to trashing Rubio, who has spent the last three days furiously attacking the GOP frontrunner in a bid to consolidate the anti-Trump wing of the party. Before the candidate took the stage, he was preceded by a string of speakers, attacking Rubio as soft on immigration and protecting American workers. At the podium, Trump spent more than half his speech trashing the Florida senator, whom he referred to again and again as “Little Marco.”

“He’s not cool. He sweats too much. And I don’t want him negotiating for us,” Trump said. “We don’t need a guy who is sweaty and scared.”